Seasonal variation in human central dopamine activity

This report focuses on two studies of seasonal variation of central dopamine activity in patients with schizophrenia and normal controls. In the two investigations, data were grouped and analyzed by season (i.e., spring-summer vs. fall-winter). The first study concerned blink rate, a putative measure of central dopamine activity; the blink rate for patients with schizophrenia was significantly increased during the spring-summer period. In the second study concentrations of catecholamines and their metabolites were measured in the hypothalamus and nucleus accumbens of normal and schizophrenic subjects. Findings include a reduced concentration of hypothalamus dopamine in normal controls and a reduced concentration of homovanillic acid in the nucleus accumbens of patients with schizophrenia, both during the spring-summer period.